High-frequency resonator tube



W. W. HANSEN HIGH-FREQUENCY RESONATOR TUBE Original Filed April 26, 1943 Oct. 3., 1950 Y 2 Sheets-Sheet 1 Oct; 3, 1950 w. w. HANSEN I Re. 23,277

HIGH-FREQUENCY RESONATOR TUBE Original Filed April 26, 1943 2 Sheets-Sheet 2 INVEA/TGA, WILL/HM M HANSEN DECEHSED BY 7145 50mm 0r Til/5755s 0;

LE L HND STH/VFORD JUN/O? UNIVERSI TY,

ATTORN EY Reissued Oct. 3, 1950 UNITED STATES PATENT OFFICE HIGH-FREQUENCY RESONATOR TUBE Original No. 2,420,314, dated May 13, 1947, Serial No. 484,648, April 26, 1943. Application for reissue July 6, 1950, Serial No. 172,395

35 Claims.

Matter enclosed in heavy brackets appears in the original patent but forms no part of this reissue specification; matter printed. in italics indicates the additions made by reissue The present invention relates generally to high frequency electron discharge apparatus having directly attached hollow resonators, and is more particularl related to velocity modulation electron discharge devices of the type disclosed in Varian Patent No. 2,242,275, issued May 20, 1941, and Hansen et al. Patent No. 2,259,690, issued October 20, 1941. The present invention is a continuation-in-part of copending Hansen and Ginzton application Serial No. 417,228, filed October 31, 1941, now Patent No. 2,391,016.

The present invention more specifically relates to modifications of the devices of the above patents wherein the evacuated portion of the discharge device is substantially confined to the electron beam path, and whereinthe frequency range of such tube structures and resonators is considerably extended.

The principal object of the present invention is to provide novel practical embodiments of high frequency tube structures using resonators in which the evacuated portion of the tube is substantially confined to the electron beam path and the resonators are made external to the evacuated portion and are adapted to be at least partially removable.

Another object of the invention is to provide improved removable resonators for use with electron beam tubes, such resonators being external to the evacuated envelope of the tube whereby a minimum amount of metal is exposed to the vacuum itself, thus eliminating sources of gases which have previously tended to decrease the life of the tube by impairing its vacuum.

Still another object of the present invention is to provide a series of interchangeable removable external resonators for such an electron beam tube, whereby the frequency range over which the device may operate may be extended greatly beyond that provided by tuning devices usuall used with such resonators.

A further object of the invention is to provide an improved cavity resonator, one element of which is removable and replaceable by an element of different size to provide a different resonant frequency,

Another object of the invention is to provide a resonator with a removable element, so designed that tuning devices and energy coupling devices may remain attached to the non-removable portion of the apparatus, and may thus be permanently connected to the device while permitting interchangeability of a part of the resonator itself, to permit change in the operating frequency of the device.

A further object of the present invention is to provide improved ultra high frequency electron discharge tube structure adapted to efficiently and conveniently operate as an ultra high frequency oscillator or receiver.

Other objects and advantages will become apparent from the specification taken in connection with the accompanying drawings wherein the invention is embodied in concrete form.

In the drawings,

Fig. 1 shows a perspective View partly in section of one embodiment of my invention.

Fig. 2 is a transverse cross sectional view of the device of Fig. 1.

Fig. 3 shows a longitudinal cross sectional view of a modification of the present invention, and

Fig. 4 is a perspective view of the removable part of the resonator of Fig. 3.

The electron tube of Fig. 1 is formed with two substantially parallel plates II and [2 of con.- ducting material, in which are inset respective electron permeable grids l3 and M, which are shown in the present instance as formed of thin radial strips which are alternately long and short, and thereby provide efficient interaction with an electron beam projected therethrough. An suitable form of electron permeable grid or electrode adapted to interchange energy with an electron beam passing therethrough may be used here. Located between plates H and I2 is a conductive cylinder l6 which carries similar grids ii and 18 in itsends. Cylinder I6 is insulated from plates H and [2 by respective insulating rings 19, and 2|, which are preferably of a material having good ultra high frequency efliciency, such as quartz or high quality ceramic material. Cylinder IE is supported by being clamped in position between plates II and 2 with insulating ring spacers l9 or 2| at either end. For this purpose, a clamping collar 22, which engages a shoulder 23 on plate 12, is fastened to plate II by means of bolts 24. It will be seen that upon tightening bolts 2% pressure is applied between collar 22 and plate H, which is transmitted to plate I2 and thereby holds cylinder l6 between insulating rings l9 and 2|.

The. interior of cylinder I6 is made part of the evacuated vessel in which the electron beam is projected. For this purpose, suitable gaskets, such as the usual lead wire gaskets 2B, are inserted between insulating rings 19, 2| and plates ll, I2 and cylinder [6. Then, upon tightening bolts 24, not only is cylinder l5 supported in 3 If desired, ordinary ceramic-to-metal seals could be used here.

Plates II and I2 effectively form conductive extensions of grids I3 and I4, respectively, and connect these grids, which are within the evacuated portion of the device, to the exterior non-evacuated portion of the apparatus. Similarly, the respective ends of cylinder I6 effectively form conductive extensions of grids l1 and I8, and connect these grids to the non-evacuated portion of the device at the exterior surface of cylinder I6. Cylinder It can be considered as having two separate functions. The first function is to serve as a portion of the evacuated envelope, and is effected by its inner surface (subject to vacuum pressure). The second function is to connect grids I1 and I8 and form part of the resonator wall, which may be considered to be effected by the outer surface of cylinder I6 (subject to atmospheric pressure), since the high frequency conduction current flow in the resonator of which cylinder I6 is a part takes place entirely on this outer surface.

The innermost portion of cylinder I6 thus serves as part of the evacuated or vacuum envelope, while the outermost portion of cylinder I6 serves as part of the cavity resonator, as will hereafter appear.

Fastened to plates II and I2 by any suitable means, such as welding or soldering, are respec-' tive tubular supports 21 and 23. Support 21 also forms a part of the evacuated vessel whose boundar is completed by glass or other insulating end bell 29 having an inwardly directed press 3I supporting a cathode 32, as is indicated somewhat schematically in the figure. Instead of having the tubular support 21 affixed to plate II, with the end bell 29 sealed thereto, the end bell 28 may be extended and held clamped against plate II, in any suitable manner, maintaining the vacuous condition of the interior of the device.

Supporting tube 28 similarly carries a target electrode or detector plate 33 by any suitable convenient means, such as a similar end bell 30. Plate 33 is preferably disposed at an angle to the axis of the device, for reasons which will be later disclosed.

In order to complete the resonant circuit or cavity resonator used with the present device, a cylindrical shell is supported between plate II and plate I2. In the present instance this shell is shown as formed of four arcuate sections in order to permit removal without disassembling the tube or impairing its evacuated condition.

These sections 34, 35, 36 and 31, when placed together, form a complete cylindrical shell which is held clamped between plate II and plate I2 by means of suitable clamping bolts 38 extending between a collar 39 hearing on plate I2 and plate II. In order that clamping and unclamping of the cylindrical shells 34 to 31 will have no effect upon the support or sealing of cylinder I6, plate I2 is made with a flexible section I2 of reduced cross-section. This may be constructed by machining down the plate I2, or by suitably fastening a thin plate I2 to the thicker central portion of plate I2. Collar 39 then bears upon the flexible section I2 and provides good electrical contact between plates II and I2 and the cylindrical sections 34, 35, 36 and 31. It Will be clear that any number of cylindrical sections may be utilized, but four have been found to be convenient.

It will be seen that by supplying a plurality of sets of these sections 34 to 31, having different eration of the device.

diameters, the size of the resonant chamber may be changed so that the operating range of the device may be appreciably extended. Also, the joints between the arcuate sections 34-31 will have no effect on the operation of the device, since these joints do not extend across the direction of current flow on the resonator walls, but are parallel to the current flow. The joints between each of the arcuate sections and plates II and I2 are more important, but harmful effects are minimized by the good contact provided by the clamping arrangement. Of course, any other desired clamping arrangement could be used. Also, if desired, insulating rings l9 and 2| could be permanently sealed to cylinder I8 and plates II- and I2, by any suitable insulator-tometal seal.

The device thus far described will, therefore, operate essentially in the samemanner as described in Patent No. 2,259,690, and by suitable choice of the accelerating voltage applied to the electron beam by means of a suitable potential source, such as indicated by battery 4!, oscillations may be set up within the resonant chamber. As discussed in this patent, for best operation the effective voltage appearing across grids I3 and I! should be less than that appearing across grids lfi'and I4. This may be accomplished by suitably selecting the relative lengths of the gaps between these pairs of grids. By the present invention, however, the relative voltages between the two pairs of grids may be adjusted so that the optimum value can be suitably selected without changing the grid spacing.

For'this purpose, a sleeve 42 is slidably mounted upon the cylinder I6, and carries a plate or flange 43 which is parallel to wall II. To-assure good electrical contact between cylinder I6 and flange 43, and to hold sleeve 42 fixed once it is adjusted, a flexible spring member 44 may be provided having spring contact with cylinder I6. By adjusting the position of flange 43 before the outer cylindrical shell is put in place, the relative capacitances and hence the effective voltages at the respective gaps may be suitably adjusted to the proper value.

Energy may be abstracted from the apparatus by means of a coupling loop 46 and an output concentric transmission line terminal 41 fixed to cylindrical shell section 34. If desired, this terminalmay be located in either plate I! or I2.

It has been discovered that during operation the electron beam passing through grids I1, i8 and cylinder I5 tends to charge up this cylinder and thereby create harmful eifects upon the op- To prevent this, a direct conductive connection for dissipating static charges is provided between flange 43 and th casing of the device by means of a coiled wire 'Ifi.

By coiling this wire 49, it remains a relatively high impedance at the ultra high frequencies involved, and, therefore, has little effect upon the field distribution within the resonator. Furthermore, wire 49 is located at or near the voltage node in the oscillating electromagnetic field within the resonator, sothat its effect upon the field is further minimized. To assure that substantially no oscillatory current flows in wire 4%, it is not directly connected to shell 34-31, but is connected to the inner conductor of a quarter-wave concentric transmission line section 5%,

whose outer conductor is connected to shell Since line 59 presents a very high, theoretically infinite, impedance'at its open'end, any current in wire 49 is further minimized.

target electrode 33.

of tube 28.

,cillations in the resonator.

In operation, the electron beam passes successively through the gapbetween grids l3 and ll, through the interior of cylinder l6, and through the gap between grids l8 and I4. During its passage through the first gap, the beam is velocity modulated by the oscillating field there present, and thereafter becomes grouped upon passage through the drift space provided by cyli'nder IE. Grids H and i8 serve to substantially completely shield the drift space from the oscillating field of the resonator. Upon passing through the second gap between grids l8 and M, the beam now gives up energy to sustainthe scillating field within the resonator. In this manner, oscillations may be generated by the device. The electrons thereafter impinge upon the This electrode may be grounded, if desired, and will then collect all the electrons of the beam. Electrode 33 is slanted so that secondary electrons will not return through grid 14, b t will be collected by the wall Pref rably, suitable cooling means, such as cooling coils wound around tube '28, are provided.

The present device may also operate as a superheterodyue converter. Thus, modulated ultra high frequency energy may be fed into the resonator of the device by way of transmission line 41 and loop 46. The frequency of the resonator, (that is, the frequency at which the device would generate oscillations) is then selected or adjusted to differ from the carrier frequency of the incoming modulated energy by just the amount of the desired intermediate frequency. Then a negative potential is applied to detector plate 33, as by means of a suitable source such as battery I49, through an output or load resistor A by-pass condenser 52 serves to by-pa-ss high frequency currents around the battery I49. The potential on detector plate 33 is so chosen that either all or substantially none of the electrons of the beam would be collected thereby in the absence of os- Then, when oscillations are supplied to the resonator, by way of the input line 41 or by the action of the electron beam,

the electrons leaving grid 14 will have higher and lower velocities than the velocity of the beam without oscillations in the resonator. If the de tector 33 is biased to just collect all the electrons of average velocity, those of lower Velocity will be repelled so that the current passing through resistor 5| will vary in accordance with the velocity of the electrons and therefore will vary in accordance with the field in the resonator. When the voltage on detector plate 33 is adjusted to just repel all average velocity electrons, then faster electrons produced by the velocity modulation in the device will be collected, while slower electrons will not. This also will serve to vary the current through resistor 5| in accordance with the variation in electron velocity.

When the modulated carrier has a frequency differing from the self-oscillatory frequenc of the device, the voltage appearing across resistor 5| will represent the modulated intermediate frequency and may be supplied to succeeding interediate frequency stages for use as desired. If

the modulated carrier has the same frequency as the self-oscillatory frequency of the device, the device will operate as a homodyne receiver and the modulation of the incoming wave will appear as a signal voltage across resistor 5| and may be utilized as desired.

The present device overcomes one of the greatestdifficulties inherent in the device of the previous Patent No. 2,259,690. In that patent, the central cylindrical conductor, corresponding to cylinder I5, was suspended or floated in a vacuum within the resonator shell. As a result, the heat unavoidablylgenerated in this cylinder by the action of the electron beam passing through the grids could not be dissipated readily, and much trouble was experienced. with burned out grids. In the presentdevice, however, the outer surface of the cylinder [6 is in the non-evacuated portion of the device and cooling air may be conducted over it for cooling purposes. This may be done in the present device by connecting one of the tubes 53 communicating with the interior of the cylindrical shells 34-31 to a suitable source of cooling fluid such as an air hose.

[Some of the features of the present invention can also be applied to regular Klystron tubes, such as of the type described in the above-mentioned Varian Patent 2,242,275 or in Varian Patent No. 2,250,511. A portion of such a device is shown in Figs. 3 and 4. These figures merely il lustrate the construction of one resonator for such a tube, it being understood that such a tube will normally utilize two such resonators in cascade, and that suitable means for projecting an electron beam successfully through the grids of these resonators and for collecting the beam will also be provided] The features of a non-evacuated external resonator portion and of demountability thereof and interchangeability of resonator parts are not limited to the type of Iclystron tube shown in Fig. 1. The features are generally useful for lclystron tubes involving one or more resonators. Varian and Hansen Patent No. 2,250,511 and Varian Patent No. 2,242,275 illustrate tube types wherein these features may be included, the evacuated envelope configuration of the principal embodiment of Varian Patent No. 2,242,275 being required to be revised to a smaller-diameter generall cylindrical form for inclusion of these features therein.

The velocity modulation tube versions shown in Patent No. 2,250,511 include annular resonator portions which are slitted for flexibility and are each attached along two junction surfaces to the grid flanges of the evacuated tube units, the interiors of these annular resonator portions being at atmospheric pressure.

A di ferent construction for the non-evacuated resonator portions from that of Patent No. 2,250,511 is shown in Figs. 3 and 4. A resonator of this type comprises several rigid parts external of the evacuated envelope instead of one flexible external portion formed of sheet metal as shown in Patent No. 2,250,511. Whereas the latter provides for a substantial tuning range by deformation of the flexible outer shell portion, the composite construction with rigid elements facilitates major frequency changes by substitution of parts. With either construction, the feature of construction and evacuation of the enlvelope containing the electron gun and the specially aligned electrodes including the plural grids is provided, whereby a given evacuated tube unit may be provided with an external resonator portion arranged according to the way in which the tube is to be used.

Where a tube is to employ more than one resonator, plural pairs'of grids may be employed in the evacuated envelope, and plural external resonator units may be arranged respectively thereon.

In Fig. 3 a portion of the evacuated envelope 7 of the device is formed'by a pair of aligned tubular members and 57 which carry respective electron permeable grids 53 and in the adjoining ends thereof. Grids t8 and 559 may be of the same type as the grids shown in Fig. 1, or of any other suitable type, and are positioned adjacent to one another to provide a relatively narrow gap therebetween. The evacuated container is maintained vacuously continuous by means of a suit able insulating ring 6i sealed between tubes 56 and 51. Fixed to tubes 55 and 5"! are respective conducting plates or rlanges 52 and 53 which are similar in function and purpose tothe plates i i and I! of Fig. 1. These plates 62 and 63 are adapted to retain a cylindrical shell 54 therebetween. Shell 64 corresponds to shell 34-31 of Fig. 1. In

this instance, shell 64 is illustrated as being formed of two semi-cylindrical sections, each being as shown in Fig. 4, and is provided with a plurality of small locating holes 66 which coact with corresponding holes in the plates 6'2 and 63, through which locating pins 6? may he passed to position shell 64 concentrically surrounding the grids 53, 59 and the electron beam.

Shell E4 is then held tightly between plates 62 and 63 by means of suitable clamps ilitstrated at 68. It is to be understood that, if desired, the clamping arrangement of Fig. 1 may be utilized here, and, conversely; the clamping arrangement 'of Fig. 3 might be used in Fig. 1, if desired. In order to prevent impairment of the seal 5! or of the joints between the tubes 56 and 51' and the plates 62 and 63, preferably one of the plates, such as 53, is provided with a section 69 having reduced cross section which will be relatively flex Y ible and will prevent the transmission of strains due to clamping. It will be seen that this flexible sectionfiii is similar in function and purpose to the section l2 of Fig. 1. Plates62 and 83 may be provided with a rality of sets of resonator shell locating holes 65 so that shells of differing diameters may be interchanged with the same apparatus to provide corresponding differing operating .frequency ranges.

In the present illustration, the output concentric line H and coupling loop 12 are fixed to the permanent wall 52 of the resonator instead of to the removable wall 34 of Fig. 1. However, either of these arrangements can be utilized, in, either Fig. 1 or Fig. 3, as desired. Also, Fig. 3 shows a type of tuning device for adjusting the resonant frequency of the resonator over a small range. For this purpose, a preferably conductive plug 13 is made adjustably insertable within the resonant cavity, as by means of a suitable threaded arrangement 14 in the wall 62, and will thereby adjust the resonant frequency of the resonator in the manner taught in the above-mentioned Hansen et al. Patent 2,259,690. It will be clear that a similar type of tuning adjustment may be provided in Fig. 1, if desired. Also, this tuning arrangement may be located in a removable wall,

but this is less advantageous.

It will be seen that Fig; 3 therefore provides a single resonator having reentrant poles formed by tubes 56 and 51 in which the grids 58 and 59 provide a relatively narrow gap for coupling the resonator with an electron beam to be passed therethrough. The particular construction here, as in Fig. 1, permits the use of interchangeable resonator shells to vary the size of the resonator and thereby vary the desired operating frequency of the device accordingly.

' Although in Figs. 3 and 4 the resonator shell 64 is shown in two separate sections, it will be understood that any suitable number of sections may be'supplied as desired. Furthermore, instead of rendering these sections entirely separable, they may be hinged together for convenience of assembly and storage. If desired or necessary, cooling fluid may be passed through the resonator to dissipate the heat generated in grids 58 and 59 in a manner similar to that shown in Figs. 1 and 2.

As many changes could be madein the above construction and many apparently Widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. Ultra-high-frequency velocity-modulation apparatus comprising a pair of spaced conductive plates having aligned apertures, an electronpermeable grid fixed within each of said apertures, a conductive cylindrical member positioned between and insulated from said plates and axially aligned with said apertures and grids, said cylindrical member supporting an electronpermeable grid at each end thereof, whereby a pair of gaps are produced, each gap being defined by a plate gridand a cylinder grid, means vacuously sealing said cylinder to each of said plates and forming part of the evacuated envelope of said apparatus, a plurality of removable conductive members forming a cylindrical shell between and connected to said plates; said shell forming a cavity resonator with said plates, grids and cylindrical member, and means adjacent one of said gaps for projecting an electron beam successively through one of said gaps, the interior of said cylindrical member and the other of said gaps, whereb ultra-high-frequency oscillations may be set up in said resonator.

2. Ultra-high-frequency velocity-modulation apparatus comprising an evacuated envelope,

- means inside said envelope for projecting an electron beam through the interior of said envelope, two pairs of electron permeable electrodes positioned in said envelope for interaction With said beam and forming two gaps to be successively traversed by said beam, each of said electrodes havingconnected conductive portions extending outside said envelope, and cylindrical conductive means connecting one electrode of each of aid pairs to an electrode of the other of said pairs and forming a cavity resonator having a pair of gaps defined by said electrodes, whereby oscillations may be set up in said resonator by the action of said beam passing successively through one of said gaps, one of said cylindrical means and the other of said gaps.

3. Ultra-high-frequency velocity-modulation apparatus comprising an evacuated envelope, two pairs of electron-permeable electrodes Within said envelope defining a pair of aligned electronpermeable gaps, conductive means exterior to said envelope and connected. to all of said electrodes and forming with said two pairs of electrodes a cavity resonator having concentrated electric field portions at said two gaps, and means in said envelope for projecting an electron beam successively through said gaps to set up oscillations within said resonator.

it. Apparatus as in claim 3, wherein said conductive means comprises a conductive shell connectingthe outer ones of said electrodes and a conductive cylinder connecting the inner ones of said electrodes, said cylinder forming a field-free drift space through which said electron beam passes between said gaps.

5. Ultra-high-frequency velocity-modulation apparatus comprising an evacuated envelope, two pairs of electron-permeable electrodes within said envelope defining a pair of aligned electronpermeable gaps, conductive means exterior to' said envelope and connected to all of said electrodes and forming with said two pairs of electrodes a cavity resonator having concentrated electric field portions at said two gaps, said conductive means comprising a conductive plate connected to each of the outer ones of said grids, and a cylindrical conductive member connecting together the inner ones of said grids, a conductive sleeve slidably mounted on and contacting said cylindrical member, a conducting flange carried by said sleeve parallel to one of said plates, whereby the electric field at one of said gaps may be adjusted by adjusting the spacing between said one plate and said flange, and means in said envelope for projecting an electron beam successively through said gaps to set up oscillations within said resonator.

6. Apparatus as in claim 3, wherein said conductive means comprises a conductive plate connected to each of the outer ones. of said electrodes and a multi-piece cylindrical conducting member removably connected between said plates and forming the outer shell of said resonator, whereby resonators of differing resonant frequency may be formed by replacing said conducting member by others of different dimensions.

7. Apparatus as in claim 3, further including means in said apparatus for adjusting the relative effective alternating voltages across said gaps.

8. Electron discharge apparatus comprising an evacuated envelope, two pairs of electron-permeable electrodes within said envelope defining a pair of aligned electron-permeable gaps, conduc tive means exterior to said envelope connected conductively to said electrodes and forming therewith cavity resonator means having said gaps as portions thereof, and means in said envelope for projecting an electron beam successively through said gaps to set up oscillations within said resonator means.

9. A high frequency tube structure comprising an evacuated insulating envelope, two pairs of spaced conducting grids within said envelope, means in said envelope for setting up an electron beam for traversing said envelope, a non-evacuated cavity resonator surrounding said envelope, said cavity resonator having interior wall means spaced from the outer walls of said resonator, said wall means and said outer walls being connected to said grids to establish a pair of regions between the pairs of grids adapted to contain alternating electric fields acting upon the electron beam, whereby one of said fields produces recurrent changes in velocity of electron beam and the other of said fields produces an inter change of energy between the beam and the resonator.

10. Electron-discharge apparatus comprising an enclosing envelope having tubular portion, means in said envelope for projecting an electron beam through said tubular portion along the thereof, a target electrode along the path of said beam for receiving said beam, and means in en-- ergy-interchanging relation with said beam comprising a pair of electrodes having closely spaced apertured portions within said tubular portion 10 defining a gap to be traversed by said beam, an a removable resonator-shell-defining means exterior to said envelope and connected to said pair of electrodes through said envelope.

11. An ultra-high-frequency super-heterodyne converter comprising cavity resonator means for confining an oscillating electromagnetic field having two separate electric field portions separated by a field-free space and having a resonant frequency, means coupled to said resonator means for supplying modulated electromagnetic energy to said resonator means having a nominal carrier frequency differing from said resonant frequency by a desired intermediate frequency, means aligned with said resonator means for passing an electron beam successively through one of said electric field portions, said field-free space and the other of said field portions, and means along the path of said beam for detecting velocity variations of said electrons aiter leaving said last field portion, whereby a correspondingly modulated intermediate-frequency wave may be derived from said detector means.

12. Electron discharge appartaus comprising a tubular evacuated envelope, a pair of electronpermeable grids within said envelope, means in said envelpe for projecting an electron beam through said grids, a pair of parallel conducting plates disposed transversely of said envelope and connected respectively to said grids, and a cylindrical shell surrounding said envelope and removably fastened between said plates and forming a cavity resonator therewith, whereby the resonant frequency of said resonator may be changed by replacing said shell.

13. A high frequency tube structure comprising an evacuated insulating envelope, a pair of spaced grid structures within said envelope, means in said envelope for setting up an electron stream for passage through said grid structures, and .a cavity resonator having a portion removably surrounding said envelope, said resonator being coupled to said grid structures, whereby a standing electromagnetic field within said resonator is caused to produce an electric field component between said grid structures acting upon said electron stream.

14. A high frequency tube structure comprising an evacuated envelope, spaced grids within said envelope, means in said envelope for setting up an electron stream for traversing said envelope and said grids, end wall members fixed upon the exterior of said envelope on oppositesides of said grids, and removable wall elements insertable between said end Wall members for forming therewith a cavity resonator adapted to contain a standing electromagnetic field having an electric fieldcomponent between said grids.

15. A high frequency tube structure as defined in claim 14 wherein tuning means is carried by one of the said fixed end wall members for effecting the tuning of said resonator. I

16. A high frequency tube structure comprising an evacuated envelope, a pair of grid structures within said envelope, means in said envelope for producing a beam of charged particles for successively traversing said grid structures, and a cavity resonator removably surrounding said envelope and conductively connected to said grid structures through the wall of said envelope, said cavity resonator being adapted to contain a standing electromagnetic field for coacting with said beam.

17. Ultra-high-frequency velocity-modulation apparatus, comprising a pair of spaced conductive plates having aligned apertures, a conductive cylindrical member positioned between said plates and axially aligned with said apertures, whereby a pair of gaps are formed, each gap being defined by one of said plates and an nd of said cylindrical member, a cylindrical shell connected to said plates and forming a cavity resonator with said plates and said cylindrical member, means aligned with said gap for projecting an electron beam successively through one of said gaps, the interior of said cylindrical member and the other of said gaps, whereby oscillations are produced within said cavity resonator, and means in said apparatus for adjusting the relative effective alternating voltages across said gaps without variation of said gaps.

18. Ultra-high-frequency velocity-modulation apparatus comprising a pair of spaced conductive plates having align-ed apertures, a conductive cylindrical member positioned between said plates and axially aligned with said apertures, whereby a pair of gaps are formed, each gap being defined by one of said plates and an end of said cylindrical member, a cylindrical shell connected to said plates and forming a cavity resonator with said plates and said cylindrical member, means aligned with said gaps for projecting an electron beam successively through one of said gaps, the interior of said cylindrical member and the other of said gaps, whereby oscillations are produced within said cavity resonator, and means for adjusting the relative effective alternating voltages across said gaps, said adjusting means comprising a conductive sleeve slidably mounted on and contacting said cylindrical member, and a conductive flange carried by said sleeve parallel to one of said plates whereby the electric field at one of said gaps may be adjusted by adjusting the spacing between said one plate and said flange.

19. Ultra-high-frequency velocity-modulation apparatus, comprising a pair of spaced conductive plates having aligned apertures, a conductive cylinder-like member positioned between said plates and. axially aligned with said apertures whereby a pair of gaps are produced, each gap being defined by one of said plates and an end of said member, means sealing said cylinder-like memher to each of said plates to form part of the evacuated envelope of said apparatus, cylindrical conductive means connected between said plates and forming a cavit resonator with said plates and cylinder-like member, and means in said envelope for projecting an electron beam succes sively through one of said gaps, the interior of said cylinder-like member and the other of said gaps, whereby ultra-high-frequency oscillations may be set up in said resonator.

20. Apparatus as in claim 19, further including means coupled to said cylinder-l ke member for dissipating electric charges accumulated by said cylinder-like member.

21. Apparatus as in claim 19, further including charge dissipating means comprising a helically wound conductor connected at one end to said cylinder-like member and having its other end forming the central conductor of a short-circuited quarter-wave concentric transmission line whose outer conductor is connected to said cylindrical means.

22. Apparatus as in claim 19, further including coaxial-transmission-line means having its outer conductor connected to said cylindrical conductive means and its inner conductor connected to said cylinder-like member.

23.. Ultra-high-frequency velocity-modulation apparatus, comprising a pair of spaced conductive plates having aligned apertures, a conductive ey lfndrical member positioned between and spaced from said plates and axially aligned with said apertures whereby a pair of gaps are produced, each gap being defined by one of said plates and an end of said member, conductive means connected between said plates and forming cavity resonator with said plates and cylindricai member, means aligned with said gaps for projecting an electron beam successively through one of said gaps, the interior of said cylindrical member and the other of saidgaps, whereby ultra.-highfrequency oscillations may be set up in said resonator, and dissipating means coupled to said cylin drical member for dissipating electric charges accumulated by said cylindrical member said dissipating means comprising a helically wound conductor connected at one end to said cylindrical member and having its other end forming the central conductor of a short-circuited quarterwave concentric transmission line whose outer conductor is connected to said cylindrical means.

24. High frequency tube structure, comprising an evacuated envelope, a pair of spaced apertured electrodes within said envelope, a cavity resonator partially removably surrounding said envelope and coupled to said electrodes whereby a standing electromagnetic field within said resonator produces an electric field component between said electrodes, and means in said enve lope for passing a stream of charged particles through said electrodes.

25. Electron-discharge apparatus, comprising means defining an enclosing vessel, means at one end of said vessel for producing an electron beam, a target electrode at the other end of said vessel, a pair of electrodes between said beam-produc= in means and said target electrode defining a gap to be traversed by said beam, a second pair of electrodes between said beam-producing means and said target electrode defining a second gap to be traversed by said beam, and a cavity resonator including conductive wall means exposed to atmospheric pressure outside said vessel electrically connecting one of said first pair of electrodes and one of said second pair of electrodes and further conductive wall means also exposed to said atmospheric pressure electrically connecting the other electrodes of said pairs.

26. Electron discharge apparatus comprising cavity resonator means providing a pair of electron-permeable gaps and adapted to enclose a standing electromagnetic field having electric field portions at said gaps, and with predetermined efiective voltages, means aligned with said gaps for projecting an electron beam successively through said portions, and means in said apparatus for adjusting the relative effective voltages across said gaps. I

27. Electron discharge apparatus comprising means defining an enclosing vessel, means at one end. of said vessel for producing an electron beam, a target electrode at the other end of said vessel, a pair of electrodes between said beam-producing means and said target electrode defining a gap to be traversed by said beam, a second pair of electrodes between said beam-producing means and said target electrode defining a second gap to be traversed by said beam, and a cavity resonator including a wall outside of said vessel electrically connecting one of said first pair of electrodes and one of said second pair of elec- 13 trodes and conductive means electrically connecting the other electrodes of said pairs.

28. Electron discharge apparatus, comprising means defining an enclosing vessel, means at one end of said vessel for producing an electron beam, a target electrode at the other end of said vessel, a pair of electrodes between said beam-producing means and said target electrode defining a gap to betraversed by said beam, a second pair of electrodes between said beam-producing means and said target electrode defining a, second gap to be traversed by said beam, and a cavity resonator outside of said vessel including means electrically connecting one of said first pair of electrodes and one of said second pair of electrodes and further including conductive means electrically connecting the other electrodes of said pairs.

29. High frequency tube structure comprisin an evacuated envelope, a source of electrons to a cavity resonator, whereby at least a portion of t e cavity resonator will surround said evacuated envelope and the electromagnetic field within within said envelope, a pair of apertured elec- Y trodes within said envelope in alignment with said source, and a further electrode in alignment with said apertured electrodes on the side there of opposite said source, said apertured electrodes having portions extending to the exterior of said envelope and adapted to be connected to a cavity resonator whereby the electromagnetic field within said cavity resonator may produce an alternating electric field between said apertured electrodes for interaction with said electrons.

30. Electron discharge apparatus comprising means including a source of electrons for producing a stream of electrons along a predetermined path, a pair of electron-permeable electrodes mounted along said path in alignment with said source and defining a narrow gap therebetween, a pair of concentric conductive means connected respectively to said electrodes and defining therewith cavit resonator means adapted to contain a standing electromagnetic field oscillating there within, and means in said apparatus for adjusting the effective voltage produced by said field across said gap, said last-named means comprising a flange member adjustably supported on the inner of said conductive means and slidable toward and away from said gap for correspondingly adjusting said effective voltage.

31. High frequency tube structure comprising an evacuated envelope, a source of electrons within said envelope, a pair of apertured electrodes within said envelope in alignment with said source, and a further electrode in alignment with said apertured electrodes on the side thereof opposite said source, said apertured electrodes including annular conductive portions surrounding said evacuated envelope and adapted to be connected to a cavity resonator in coaxial relation therewith whereby the electromagnetic field within said cavity resonator may produce an alternating electric field between said apertured electrodes for interaction with said electrons.

32. High frequency tube structure comprising an evacuated envelope, a source of electrons within said envelope, a pair of apertured electrodes within said envelope in alignment with said source, and a further electrode in alignment with said apertured electrodes on the side thereof opposite said source, each of said apertured electrodes comprising a grid provided with a peripheral flange, the flange being sealed in the evacuated envelope and having an annular portion exterior of said envelope adapted to be connected iii) said cavity resonator may produce an alternating electric field between said apertured electrodes for interaction with said electrons.

33. High frequency tube structure comprising an evacuated envelope having a generally cylindrical portion comprising alternate glass and metal annular sections, a source of electrons within said envelope, a pair of apertured electrodes within said envelope in alignment with said source, and a further electrode in alignment with said apertured electrodes on the side thereof opposite said source, said apertured electrodes comprising first and second grids inside said envelope connected respectively to two of said metal annular sections separated by a glass annular section, said apertured electrodes being thereby adapted to be connected to a cavity resonator whereby the electromagnetic field within said cavity resonator may produce an alternating electric field between said apertured electrodes for interaction with said electrons.

34. High frequency tube structure comprising an evacuated envelope having a generally cylindrical portion comprising alternate glass and metal annular sections, a source of electrons within said envelope, a pair of apertured electrodes within said envelope in alignment with said source, and a further electrode in alignment with said apertured electrodes on the side thereof opposite said source, said apertured electrodes comprising first and second grids inside said envelope spaced apart by a dimension appreciably smaller than their diameters and connected respectively to two of said metal annular sections separated by a glass annular section, said apertured electrodes being thereby adapted to be connected to a cavity resonator whereby the electromagnetic field within said cavity resonator may produce an alternating electric field between said apertured electrodes for interaction with said electrons.

35. High frequency tube structure comprising an evacuated envelope having a generally cylindrical portion comprising alternate glass and metal annular sections, a pair of apertured electrodes within said envelope in alignment with said source, and a further electrode in alignment with said apertured electrodes on the side thereof opposite said source, said apertured electrodes comprising first and second grids inside said envelope connected respectively to two of said metal annular sections separated by one of said glass annular sections, said two metal annular sections including substantially parallel circular flanges of substantially equal diameters, said apertured electrodes being adapted for connection through said two metal annular sections to a cavity resonator whereby the electromagnetic field within said cavity resonator may produce an alternating electric field between said apertured electrodes for interaction with said electrons.

THE BOARD OF TRUSTEES OF LELAND STANFORD JUNIOR UNIVERSITY, Assignee, by Mesne Assignment, of William W.

Hansen, Deceased, By A. E. BRANDIN,

Business Manager, Leland Stanford Junior University.

(References on following page) 15 REFERENCES CITED The following references are of record in the file of this patent or the original patent:

UNITED STATES PATENTS Number Name Date Boddie Nov. 6, 1934 Samuel June 16, 1936 Hahn Nov. 26, 1940 Hahn Nov. 26, 1940 McArthur Mar. 18, 1941 Number Name Date Varianet a1. May 20, 1941 Ryan May 27, 1941 Maslov Aug. 19, 1941 During Sept. 2, 1941 Hansen et a1 Oct. 21, 1941 Mouromtsefi et a1. Nov. 18, 1941 Samuel May 5, 1942, Samuel Dec. 22, 1942 Litton Feb. 2, 1943 

